The objective of this proposal is to investigate sophisticated radiopharmaceuticals bearing positron radionuclides for the purpose of developing superior radiodiagnostic agents for positron tomography imaging of organs containing neoplastic diseases. The studies will include: 1. The improvement of 13N-glutamate and 13N-asparagine preparations. 2. The syntheses of 13N-glutamine, 11C-methionine, N-11CH3-L-phenylalamine N-11CH3-L-DOPA, and 3-18FDG. 3. The preparation of the radiolabeled agents in pure and sterile forms. 4. The performance of animal studies with 13N-glutamate, 13N-asparagine, 13N-glutamine and 11C-methionine and N-11jCH3-L-phenylalamine for pancreas imaging in conventional and tomographic mode. 5. Measurement of relative incorporation of N-11CH3-L-DOPA into Cloudman 91 melanoma cell lines, and human melanoma cell lines, compared to normal fibroblast lines. Animal imaging studies will also be carried out. 6. Quantitative imaging of skeletal pathology in animals following 18F-fluoride administration. 7. Measurement of animal tumor uptake and imaging with substrates of metabolism such as labeled glucose analogs and labeled amino acids. The development of "physiological" radiolabels with specific metabolic pathways will aid in determining the functional status and morphology of organs containing neoplastic diseases.